Introduction: Pyometra is the collection of pus in the uterine cavity due to occlusion of the endocervical canal. Spontaneous perforation of pyometra and subsequent diffuse peritonitis is a very rare, but life-threatening complication.

Case report: We report a rare case of peritonitis with a pyoperitoneum in an elderly female, which was caused by a spontaneous perforation of pyometra. A 70-year-old P7 postmenopausal female presented in the emergency department with signs of diffuse peritonitis. Contrast-enhanced computed tomography (CECT) abdomen showed infective pathology of uterus with rupture. At laparotomy, about 400 mL of pus was found in the peritoneal cavity and a rent of about 2 × 1 cm was present on the fundus of the uterus. Peritoneal lavage, total abdominal hysterectomy, and salpingo-oophorectomy were performed. She was discharged on the 14th postoperative day (POD) without any major complication. Histopathology showed atrophic endometrium with severe endometritis and no e/o malignancy and cervix showed chronic cervicitis.

Conclusion: Spontaneous rupture of pyometra is very rare, but should be considered as a differential diagnosis in elderly postmenopausal women presenting with acute abdomen.